Author:

Dennis Drew(CNAM, Physics Department, Universtity of Maryland)

Topological insulators (TI) are a predicted new quantum state of matter in
which spin-orbit coupling gives rise to topologically protected surface
states with unpaired spin-helical Dirac cones. TIs are predicted to have
exotic properties including Majorana fermions induced by the proximity
effect from a superconducting film, a intrinsic magnetoelectric effect and
hybridized spin-plasmon modes. The magneto-electric effect leads to Faraday
and Kerr rotations quantized in units of the fine structure constant. This
effect corresponds to $\raise.5ex\hbox{$\scriptstyle 1$}\kern-.1em/
\kern-.15em\lower.25ex\hbox{$\scriptstyle 2$} $ integer quantum Hall step
and is predicted both in field and \textbf{\textit{in the absence of a
magnetic field when magnetic order gaps the Dirac spectrum}}. A key
difference between this half integer QHE in TIs and the usual integer QHE is
that the former cannot be measured by a dc transport experiment. I will
describe experiments designed to measure the Kerr rotation in Bi2Se3, one
example of a topological insulator. Gating the surface isolates the surface
response from the bulk signals due to unavoidable bulk carriers from defects
and impurities. Preliminary results will be presented on the surface state
Kerr rotation for Bi2Se3 doped with Mg (ungapped) and Bi2Se3 doped with Sm
(magnetically gapped).

*Work supported by DOE (Contract No.DE-SC0005436).

To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2012.MAR.B27.1